Case IH 3841 – Engine ECU: Temperature Sensor Circuit (T2) Downstream Oxicat - Low Error

The control module is receiving a signal voltage from the exhaust gas temperature sensor (located downstream of the oxidation catalyst / upstream of the DPF) that has fallen below the minimum acceptable threshold. This typically points to a short circuit to ground in the sensor's wiring harness, a failed sensor pulling the voltage down, or an open circuit.

• skid steer
• Case IH Skid Steer Loaders (SSL) (e.g., SR200, SV300)
• Case IH Compact Track Loaders (CTL)
• Case IH Farmall Tractors (e.g., Farmall 75A, 115U)

1. 1

   Visually inspect the T2 temperature sensor wiring harness and connector for melted insulation, chafing, or corrosion.

2. 2

   Disconnect the sensor, turn the key ON, and check the harness side for a 5V reference signal from the Engine ECU and a solid ground.

3. 3

   Measure resistance across the sensor's pins to check for a dead short (0 ohms) or an open circuit (infinite ohms).

1. 1

   Cool Down

   Ensure the machine is turned off and the exhaust system has completely cooled to prevent severe burns.

2. 2

   Locate the Sensor

   Find the T2 Exhaust Gas Temperature sensor. It is threaded into the exhaust piping downstream of the Diesel Oxidation Catalyst (DOC) and upstream of the DPF.

3. 3

   Disconnect

   Unplug the electrical connector linking the sensor to the engine wiring harness.

4. 4

   Removal

   Use a wrench or specialized sensor socket to carefully unscrew the sensor from the exhaust pipe. Note: Exhaust sensors frequently seize due to heat cycling; applying penetrating oil to the threads and allowing it to soak may be necessary.

5. 5

   Preparation

   Apply a small amount of high-temperature anti-seize compound to the threads of the new sensor (if it does not come pre-applied). Be extremely careful not to get any anti-seize on the sensor probe itself, as this can contaminate it.

6. 6

   Installation

   Thread the new sensor into the exhaust pipe by hand to prevent cross-threading, then tighten it to the manufacturer's specification (typically around 45 Nm / 33 lb-ft).

7. 7

   Reconnect

   Plug the sensor's electrical connector back into the engine harness.

8. 8

   Clear Codes

   Use the Case IH Electronic Service Tool (EST) or a compatible heavy-duty scan tool to clear the 3841 fault code from the Engine ECU. Run the engine to operating temperature to verify the code does not return.